Poizner, the state insurance commissioner, spent three hours touring the border area and meeting with Border Patrol officials followed by a press conference on the pedestrian bridge over I-5 that overlooks the San Ysidro border crossing just inside the United States.

As governor he said he would redeploy the National Guard to help patrol the border, shut off public benefits to people who are not in the country legally and revoke the business licenses of employers who hire them.

“I’m convinced that you can’t build a wall long enough or a fence high enough,” Poizner said. “In order to address the problems with people coming in here illegally — and it is a serious problem facing the state of California — we have to turn the magnets off.”

Poizner and his Republican opponent, former eBay CEO Meg Whitman, both began running campaign advertisements on Monday attacking each other on illegal immigration.

The Poizner television ad assails Whitman for supporting “Obama’s amnesty plan” and for opposing the new Arizona law that allows law enforcement officers to verify the citizenship status of people suspected of being in the country illegally.

A Whitman radio ad admonishes voters, “don’t be fooled by misleading ads” and says she is “100 percent against amnesty for illegal immigrants.”